Bus driver circuit signal speeds have increased over time, requiring reliable and faster bus signal transitions to a desired voltage level. Bus driver output signals are measured at the time of manufacture, during maintenance, and during troubleshooting to ensure proper circuit performance. The measurements usually require that an external test board be attached to the circuit board upon which the bus driver circuitry is disposed. Connecting wires or lead lines are soldered or otherwise attached and detached between the test board and the circuit board. Test probes are used to make transitory electrical contact with pins or test pads. Test probe use necessitates conveniently located and sized test points on the test board. Proper measurement techniques include isolating the signal under test by taping off certain lead lines. The process is prone to problems with impedance matching and ground loops. The taped off lead lines become stubs and introduce undesirable effects within the circuitry, such as ringing and electromagnetic interference, which affects the accuracy of the measurements. The addition of test probe capacitance, wiring, and external board capacitance compromises the measurements. Furthermore, the current process is time consuming, cumbersome, and poses risks of damage to circuitry on the circuit board under test. Also, test loads have had to include capacitors of smaller value to accommodate the increased speed of performance.
Therefore, it would be desirable to provide a test method for a bus driver signal that accurately and reliably measures signal performance and facilitates connection with an external measurement device.